Any chemicals that have a useful function in the production, processing, or preservation of foods or drinks may nevertheless be toxic, and possiblymutagenic orcarcinogenic. For this reason, food additives and contaminants, such as traces of chemicals used in industrial agricultural production, are subject to international and national surveillance and regulations.
They are a cause for concern and vigilance because some, and in particular agricultural chemicals, are known to be toxic in experimental settings, though at levels well above those found in foods and drinks.
There is little epidemiological evidence on the possible effects of contaminants and additives as present in foods and drinks.
Because contaminants and additives are subject to international and national regulation, there is a vast amount of toxicological information from experiments on laboratory animals and other settings. Failing any other method, it seems reasonable to observe the effects of food additives and contaminants on laboratory animals at levels greatly in excess of any likely to be present in foods and drinks; and based on several assumptions and judgements, to set limits for safety in use. When such limits are used as regulatory limits, they are also subject to surveillance and special investigation when any chemical present in foods and drinks seems to be a cause for special concern.
This are remains controversial. Theoretically, it would be ideal if food supplies contained no trace of any toxic substance, including those that are or may be mutagenic or carcinogenic. However, some foods in nature contain carcinogens and the issue is not confined to methods of industrial food processing.
-aadautech, a cancer drug discovery and therapeutics blog